For the last few months, we've been covering the Blumhouse Productions adaptation of Stephen King’s Gramma. Titled Mercy, the movie has already started filming, but we have news of a late addition to the cast.

Mark Duplass has joined the project in an unspecified role, according to a report from Deadline. Duplass (pictured above) is known for his work on The League, and has also appeared in Safety Not Guaranteed, Zero Dark Thirty, and The Mindy Project.

Mercy is currently in production with a cast that includes Dylan McDermott, Frances O’Connor, Chandler Riggs, Joel Courtney, Shirley Knight and Chris Browning. The movie is being directed by Peter Cornwell (The Haunting in Connecticut) from a script written by Matt Greenberg (1408).

Gramma was first published in Weirdbook magazine and was part of 1985′s Skeleton Crew. The story “follows two young boys who go with their single mother to take care of their elderly, senile grandmother named Mercy, only to discover that she’s a witch who made a pact with a dark force many years before.”

Mercy is one of multiple Stephen King projects currently moving forward. CBS is developing a TV series based on Under the Dome, Tom Holland is directing The Ten O’Clock People, an adaptation of Cell with John Cusack is in the early planning stages, and a remake of Carrie will hit theaters this October.